The present invention relates to an apparatus in a paper machine for guiding the transverse position of a fabric, such as a drying wire, a press felt, or an equivalent fabric, and includes an alignment roll for the fabric. The axial alignment of the alignment roll is regulated by means of a guide apparatus, which comprises a sledge or equivalent arranged in connection with one or both of the bearing supports of the alignment roll. The position of the sledge or equivalent in relation to the frame part of the apparatus is regulated by means of an actuator motor.
Prior art wire guide apparatuses that are commonly used comprise a pneumatic bellows device arranged in connection with a bearing support of the alignment roll so that the axial alignment of the alignment roll can be altered, and the transverse position of the fabric can be regulated. In this respect, regarding the prior art related to the present invention, reference is made to the assignee's Finnish Patent No. 77,434 (corresponding to U.S. Pat. No. 4,932,578, the specification of which is hereby incorporated by reference herein).
It is a drawback of prior art bellows devices in a guide apparatus used for axial regulating the alignment roll that the height of the apparatus is quite large, and it is difficult to make the apparatus rigid enough, which causes problems, e.g., vibration. It is a further drawback of the prior art devices, that in the event of a failure in the supply of electricity, or of any other disturbance, the pressure is lost in the bellows, in which case the apparatus is usually shifted to one of its extreme positions. As a result, the fabric guided by the apparatus is guided to the side and is usually completely destroyed.
It is also a drawback of the prior art apparatuses for guiding a drying wire that the pneumatic bellows of the actuator have poor resistance to the temperatures present in the dryer section.
It is a further drawback of the prior art apparatuses that the position of their location is usually limited because the guides of the displaceable sledge of the guiding apparatus, the bearing support of the alignment roll being attached to this sledge, can be loaded in certain directions only.
It is another drawback of the prior art apparatuses that there is a considerable distance between the guides of the sledge and the area of action of the bellows devices. This produces torsion in the guides of the sledge with resulting detrimentally high friction forces, which make precise adjustment of the position even more difficult.